TITLE:   GCN CIRCULAR
NUMBER:  23428
SUBJECT: GRB 181120A: Fermi GBM observation
DATE:    18/11/20 21:19:58 GMT
FROM:    Cori Fletcher at USRA/NASA  <corinne.l.fletcher@nasa.gov>

C. Fletcher (USRA) and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi GBM Team:

"At  06:21:19.08 UT on 20 November 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 181120A (trigger 564387684 / 181120265),
which was also detected by the LAT (Bissaldi et al. 2018, GCN 23427)
The GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 71 degrees.

The GBM light curve shows a single bright pulse followed by extended emission
with a duration (T90) of about 17 s (50-300 keV).
The time-averaged spectrum from T0-0.5 s to T0+16.9 s is best fit by
a power law function with an exponential
high-energy cutoff.  The power law index is -0.95 +/- 0.08 and
the cutoff energy, parameterized as Epeak, is 158 +/- 14 keV

The event fluence (10-1000 keV) in this time interval is
(4.60 +/- 0.191)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.1 s in the 10-1000 keV band
is 11.5 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."